Annealing furnace for coil material



June 23, 1970 suKEHARU ENDO ANNEALING -FURNACE FOR COIL MATERIAL FiledJune 18, 1968 Sheets-Sheet l INVENTOR SUKEHARU ENDO BYVM f7/J ATTORNEYS`une 23, 1970 SUKEHARU ENDO 3,516,649

ANNEALING FURNACE FOR COIL MATERIAL Filed June 18. 1968 4 Sheets-Sheet 2lllllrv- June 23, 1970 suKEHARu ENDO 3,516,649

ANNEALING FURNACE FOR COIL MATERIAL Filed June 18, 1968 4 Sheets-Sheet 5,Huhn

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INVENTOR SUKEHARU ENDO BY 77,@ W/ @Zi ATTORNEYS June 23, 1970 suKr-:HARUENDO 3,516,649

ANNEALING FURNACE FOR COIL MATERIAL Filed June 18, 1968 4 Sheets-Sheet4.

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United States Patent O1 ce 3,516,649 Patented June 23, 1970 ANNEALINGFURNACE FOR COIL MATERIAL Sukeharu Endo, Yokohama-shi, Japan, assignerto Ishikawajima-Harima Jukogyo Kabushiki Kaisha,

Tokyo-t0, Japan, a Japanese company Filed June 18, 1968, Ser. No.737,878 Int. Cl. F27b 11/14 U.S. Cl. 263-40 1 Claim ABSTRACT OF THEDISCLOSURE The present invention relates to an annealing furnace. In thefurnace, coils covered with a heating cover are directly heated byradiant tubes arranged on both top and bottom.

An object of the present invention is to improve the batch type coilannealing furnace for cold-rolled steel sheet.

According to the prior art, this kind of batch type annealing fumaceuses an inner cover with which to protect the work, that is heatedindirectly by heating the said inner cover externally.

To be more precise, burners or radiant tubes or in some cases heatingelements are used for heating the said inner cover that heat theprotective gas circulated in the said inner cover that transfers heat tothe coil ends that further transmit heat to its central part byconduction.

Since the heat transmission to the coil center enlists conduction,heating speed is naturally confined by the thermal conductivity of thematerial to be heat-treated.

In order to reduce the overall heating cycle, it will be required, ofnecessity, to accelerate the heating of coil ends up to a desiredtemperature.

The conventional furnace has the disadvantage of taking extremely longhours to heat the coil ends up to a prescribed temperature, because thecoil ends are heated indirectly through the inner cover and theprotective gas which requires a long time to transfer the necessarycalorie.

The conventional furnace heat-treats 3-4 coils stacked in the innercover usually. For this reason, it has another disadvantage of invitingstickings on the lower coils due to weight of coils, especially in caseof very thin strip coils, causing a poor yield.

On the other hand, if one coil only is heat-treated to avoid the abovedemerit, it will degrade productivity and cost much.

Therefore, if a single-stack coil can be heated rapidly at its bothends, it could cause higher yield with less cost.

The so-called speed cycle furnace developed a few years ago is a furnaceto heat and anneal a single-stack open coil by direct radiant tubes, andis not intended for heating tight-coil uniformly.

In this conventional furnace, the radiant tubes are arranged only on theupper part of the coil.

The heating capacity of coil annealing furnace is expressed by dividinga charge weight by the time required for heating the coil center up to aspecified temperature, provided that coil temperatures be held within aspecified range.

It should also be noted that the coil end temperature must 'not beincreased beyond the upper limit of the prescribed temperature rangebecause, it could otherwise cause the work to be degraded.

In the meantime, the heating speed is diversely affected by the coil endtemperature because heat transmission is carried out by conductionthrough coil ends.

Accordingly, to increase heating capacity is bound to be the only meansin which the coil end temperature can attain a level much closer to theupper limit of the appoint temperature range without loss of time.

The object of the present invention is to uniformly heat up the coilends by means of radiant tubes provided on both the upper and lowerparts 0f the coil.

Since the heating furnace of the present invention is of the directradiation type using a radiant tube as against the conventional methodin which protective atmospheres are used without exception for heatingcoils by convection, its heating speed is very high and uniform heatingcan be ensured if the radiant tubes can be arranged close to the coilends.

Detailed hereunder is the present invention with reference to theaccompanying drawings in which:

FIG. l Shows a conventional coil annealing furnace.

FIG. 2 shows a section illustrating the construction scheme of theannealing furnace according to the present invention.

FIG. 3 shows sections A-A and C-C in F-IG. 2.

FIG. 4 shows sections as viewed from the directions C, D, E and F,respectively.

FIG. 5 is an illustrative drawing showing the relationship between coiland plenum chamber located inside the annealing furnace according to thepresent invention.

As can be seen in FIG. 1, the conventional coil annealing furnace iscomposed of: diffuser 7 having circulating fan 8, convector plates 5 andcoils 6 piled alternately in 3 to 4 stacks on the said diffuser 7, base10 `and inner cover 4 put on the said base 10 to seal out open air,motor 9 for driving the said circulating fan 8, sand seal 11 to seal thesaid inner cover 4, heating cover 1 to be put on the above-mentionedinner cover 4 at the time of heating the said coil 6, and burner 2located at the lower part for heating the said inner cover 4.

In this system, the said inner cover is filled up with protective gasthat is circulated in the arrow direction by the said fan 8 and givenheat from the said cover 4 and communicates heat to the ends of the saidcoil 6 in the course of passing through the said convector plates 5.

Namely, in the conventional coil annealing furnace, the coil 6 is heatedthrough the two media, the inner cover 4 and the protective gas.

As illustrated in FIG. l, since the coil 6 should take a considerablylarge compressive force due to their selfweight because coils are piledin 3 to 4 stacks, coil ends and convector plates 5 might be Welded.

This failure is liable to occur especially in case of thin coil.

Part 3 appearing in the figure indicates a chimney provided on theheating cover 1.

Shown in FIGS. 2 4, 6 and 7 is the coil annealing furnace according tothe present invention to improve the conventional type.

According to the present invention, the annealing furnace is providedwith various means: plenum chamber 31 in which radiant tubes 23 may beinstalled on the base 26 (coil 30 to be installed on the said chamber 31as shown by way of example in FIG. 5), circulating fan 27, base 26provided with the said fan 27 on its side wall, heat exchanger 2S whichcan be taken as far out as the outlet on the upper part of the saidcirculating fan 27 at the time of cooling operation, ducts 40, 41 madeof heat resistant steel connecting the said chamber 31 and the said heatexchanger 25 to the said fan 27, heating cover 21, radiant tubes 22provided on the ceiling of the said heating cover 21, bafe 24 forrectifying the stream of protective gas, seal mechanism 29 to be usedfor the said heating cover 21, motor 28 for driving the said circulatingfan 27, upper air manifold 32, upper gas manifold 3'3, lower gasmanifold 35, lower air manifold 34, worm type reduction gear 36, supportrollers 37 for the said heat exchanger 25, burner 38 and furnace oorsupport column 39.

In this system, the ends of coil 30 can be directly heated by theradiant tubes 22 installed on the heating cover 21 as well as by theradiant tubes 23 installed on the base 26.

These upper and lower radiant tubes 22 and 23 are temperature-controlledindependently of each other, whereby both the upper and lower ends ofcoil can be protected from being overheated and can also be maintainedat a constant temperature.

Since the coil ends are heated directly by radiation, the temperaturerise of the coil 30 is made quick, resulting in the reduction of heatingtime.

When the furnace operation enters the cooling cycle, the combustion isstopped and the heat exchanger is put in the furnace to cool down thecirculating gas which cools the coil 30. This cooling method has anextremely shortened cooling cycle as compared with the conventionalmethod in which the inner cover is air-cooled, because it uses watercooled pipes in its heat exchanger.

On the other hand, since the coil annealing furnace according to thepresent invention can be large-sized, it can accommodate various coils.Therefore, there is no limit to the coil dimensions and no decline inprocessing capacity due to limitation to charge weight.

In addition, there is no fear of sticking because coil bottom takes assmall a weight as l/s-lt of the total weight by the virtue of asingle-stack system.

This involves that the coil annealing furnace according to the presentinvention is most suited to the heat treatment of very thin coil.

As will be clear in the foregoing, since the coil annealing furnaceaccording to the present invention is able to heat-treat a single-stackcoil directly by radiant tubes arranged uniformly on both the upper andlower sides of the coil without inner cover, its heating time is sharplyreduced as compared with the conventional annealing furnace, and itstemperature uniformity is excellent.

In addition, because the load applied on the bottom of the coil isreduced to l/s-Mx, there is no fear of incurring sticking even on a verythin strip coil.

Furthermore, since the present furnace is equipped with the movable heatexchanger, the cooling cycle is also reduced by a large margin, which inturn mitigates overall heat processing.

This means quick delivery, high productivity and low housing heightbecause of low furnace height.

Since the present furnace dispenses with consumables such as an innercover, material handling is greatly alleviated and manpower can bereduced to the minimum, resulting in a most economical operation.

What is claimed is:

1. A furnace adapted to anneal coils, comprising a plenum chamber denedby a base and a heating cover, a first set of radiant heating pipesmounted over the base and in close proximity thereto, a second set ofradiant heating pipes mounted lbeneath the top of the cover and spacedabove the first set of radiant heating pipes, adjustable baffles mountedin a zone between the top of the cover and the second set of radiantheating pipes, a blower mounted in the chamber at about the level of therst set of radiant heating pipes, a first duct communicating with theblower and opening in close proximity to an extremity of the first setof radiant heating pipes, a second duct communicating with the blowerand opening below the level of the second set of radiant heating pipes,a heat exchanger adjustably mounted in an opening through the heatingcover, the heat exchanger being reversibly adjustable from a position inclose proximity to an extremity of the second set of radiant heatingpipes and with an extremity of the heat exchanger being in communicationwith the opening of the second vduct and an opposite extremity of theheat exchanger being in communication Iwith the zone between the top ofthe cover and the second set of radiant heating pipes to a position inwhich the heat exchanger is retracted from the chamber, the blower beingsubstantially axially aligned with the rst duct and a plane passingthrough the first set of radiant heating pipes and being substantiallyradially aligned with the second duct, and means for supporting aplurality of coils, in side by side relationship and with their axesupright, between the first and second sets of radiant heating pipes,whereby rotation of the blower is adapted to circulate a gas up throughthe second duct, past the heat exchanger when it is in its non-retractedposition, above the second set of radiant heating pipes, downward withthe assistance of the bafiies to and through the coils and finally pastthe first set of radiant heating pipes and through the first duct backto the blower.

References Cited UNITED STATES PATENTS 2,479,102 8/ 1949 Dailey 263-402,638,889 5/1953 DoW.

2,713,480 7/1955 Ruckstahl 266-5 2,955,062 10/1960 Cullen et al. 266-52,983,502 5/1961 McClure 263-40 3,032,326 5/ 1962 Hepburn.

3,301,541 1/1967 Ipscn 263-40 JOHN I CAMBY, Primary Examiner

